What do you dress them in for sleep during the winter months?

LO is too old to be swaddled and doesn't like sleep sacks. We've been putting her in footed PJ's and keep her room at around 70 degrees but I worry she might be cold at night. I have thought about a onesie under her PJ's but then I worry about overheating. I realize now that I'm sounding neurotic! It's so hard when they're too young to tell you if they're comfortable!